Year 9 Cambridge Computer Science: Unit Test Mock Exam Walkthrough | Year 9 剑桥计算机科学：单元测试模拟卷解析

📚 Year 9 Cambridge Computer Science: Unit Test Mock Exam Walkthrough | Year 9 剑桥计算机科学：单元测试模拟卷解析

This article takes you through a typical Year 9 Cambridge Computer Science unit test mock paper, offering worked solutions and key exam strategies for every topic. Use it to revise data representation, logic, algorithms, Python programming, hardware and cybersecurity.

本文带你完整体验一份典型的 Year 9 剑桥计算机科学单元测试模拟卷，为每个主题提供详细解答和关键考试策略。用它来复习数据表示、逻辑、算法、Python 编程、硬件和网络安全。

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1. Data Representation: Binary to Decimal | 数据表示：二进制转十进制

One of the most fundamental skills is converting binary numbers into decimal. Let us take the binary number 1011₂ as an example.

最基础的技能之一是把二进制数转换为十进制。我们以二进制数 1011₂ 为例。

(4) and 2³ (8). Multiply each binary digit by its place value: 1 × 8, 0 × 4, 1 × 2, 1 × 1.

从右到左写出位值：2⁰ (1)、2¹ (2)、2² (4) 和 2³ (8)。将每个二进制数字与其位值相乘：1 × 8、0 × 4、1 × 2、1 × 1。

Add the results: 8 + 0 + 2 + 1 = 11. Hence, 1011₂ equals decimal 11.

把结果相加：8 + 0 + 2 + 1 = 11。因此 1011₂ 等于十进制 11。

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2. Hexadecimal Conversions | 十六进制转换

Hexadecimal uses base 16, where digits 10–15 are represented by letters A–F. To convert hex 2F₁₆ to decimal, multiply each digit by its power of 16.

十六进制使用基数为 16，数字 10–15 用字母 A–F 表示。要把十六进制 2F₁₆ 转换成十进制，将每一位乘以 16 的幂。

The digit '2' is in the 16¹ place, and 'F' (value 15) is in the 16⁰ place. Calculation: (2 × 16) + (15 × 1) = 32 + 15 = 47.

数字 '2' 在 16¹ 位，'F'（值为 15）在 16⁰ 位。计算：(2 × 16) + (15 × 1) = 32 + 15 = 47。

00 decimal to hex divide by 16: 200 ÷ 16 = 12 remainder 8. 12 is C, so the result is C8₁₆.

反方向转换时，要把十进制 200 转为十六进制，除以 16：200 ÷ 16 = 12 余 8。12 是 C，因此结果为 C8₁₆。

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3. Logic Gates and Truth Tables | 逻辑门与真值表

Logic gates form the basis of digital circuits. The expression (A OR B) AND NOT C, written as (A ∨ B) ∧ ¬C, can be analysed with a truth table showing all input combinations.

逻辑门构成数字电路的基础。表达式 (A OR B) AND NOT C，写作 (A ∨ B) ∧ ¬C，可以通过显示所有输入组合的真值表进行分析。

there are 2³ = 8 rows. Intermediate columns help us compute the final output step by step.

对于三个输入，共有 2³ = 8 行。中间列帮助我们逐步计算最终输出。

A	B	C	A ∨ B	¬C	(A ∨ B) ∧ ¬C
0	0	0	0	1	0
0	0	1	0	0	0
0	1	0	1	1	1
0	1	1	1	0	0
1	0	0	1	1	1
1	0	1	1	0	0
1	1	0	1	1	1
1	1	1	1	0	0

The output is 1 only when A or B is 1, and C is 0. This is exactly what the expression (A ∨ B) ∧ ¬C describes.

只有当 A 或 B 为 1 并且 C 为 0 时输出才为 1。这正是表达式 (A ∨ B) ∧ ¬C 所描述的情况。

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4. Computer Architecture: CPU Components | 计算机体系结构：CPU 组件

A typical exam question asks you to name the main components of the central processing unit and explain their roles.

典型的考题要求你写出中央处理器的主要组件并解释它们的作用。

The control unit (CU) coordinates all activities of the CPU by sending control signals to fetch, decode and execute instructions.

控制单元 (CU) 通过发送控制信号来协调 CPU 的所有活动，完成取指、译码和执行指令。

The arithmetic logic unit (ALU) handles all arithmetic (+, –, ×, ÷) and logical (AND, OR, NOT) operations.

算术逻辑单元 (ALU) 处理所有算术运算（+、–、×、÷）和逻辑运算（AND、OR、NOT）。

Registers are extremely fast memory locations inside the CPU; they hold data currently being processed, such as the instruction being executed and intermediate results.

寄存器是 CPU 内部速度极快的存储位置；它们保存当前正在处理的数据，比如正在执行的指令和中间结果。

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5. Memory and Storage Units | 内存与存储单位

RAM is volatile primary memory that stores data and programs currently in use. ROM is non‑volatile and holds firmware, such as the boot program.

RAM 是易失性主存，存储当前使用的数据和程序。ROM 是非易失性存储器，保存固件，比如引导程序。

1 KB = 1024 bytes, 1 MB = 1024 KB, 1 GB = 1024 MB. For example, 4 GB = 4 × 1024 = 4096 MB.

数据存储单位遵循 2 的幂：1 字节 = 8 比特，1 KB = 1024 字节，1 MB = 1024 KB，1 GB = 1024 MB。例如，4 GB = 4 × 1024 = 4096 MB。

Secondary storage devices such as SSDs and HDDs provide long‑term, non‑volatile storage. Optical discs and USB flash drives are also common examples.

辅助存储设备如 SSD 和 HDD 提供长期、非易失性的存储。光盘和 U 盘也是常见的例子。

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6. Input and Output Devices | 输入输出设备

Input devices allow users to send data to the computer. Examples include a keyboard, mouse, barcode reader, microphone and touchscreen.

输入设备允许用户将数据发送到计算机。例子包括键盘、鼠标、条码阅读器、麦克风和触摸屏。

Output devices present information from the computer to the user. Monitors, speakers, printers and headphones are typical output devices.

输出设备将计算机的信息呈现给用户。显示器、扬声器、打印机和耳机是典型的输出设备。

Some devices work both ways. A touchscreen acts as an input device when touched and as an output device when displaying information.

有些设备可以双向工作。触摸屏在被触摸时充当输入设备，在显示信息时充当输出设备。

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7. Algorithms and Flowcharts | 算法与流程图

An algorithm is a step‑by‑step procedure for solving a problem. Flowcharts use standard symbols to represent algorithms visually.

算法是解决问题的分步过程。流程图使用标准符号来可视化地表示算法。

Ovals mark the start and end. Parallelograms show inputs and outputs. Rectangles represent processing steps, while diamonds indicate decisions (yes/no).

椭圆标记开始和结束。平行四边形表示输入和输出。矩形表示处理步骤，菱形表示判断（是/否）。

For example, an algorithm to find the largest of two numbers would use a diamond to compare them and a rectangle to assign the larger value to a variable.

例如，找出两个数中较大值的算法会用菱形比较两者，用矩形将较大值赋给变量。

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8. Pseudocode and Trace Tables | 伪代码与追踪表

Pseudocode describes an algorithm using structured English that resembles programming code. Trace tables help track variable values as the algorithm runs.

伪代码使用结构化的、类似程序代码的英语来描述算法。追踪表有助于在算法运行时跟踪变量的值。

Consider this pseudocode:

考虑以下伪代码：

x ← 3
y ← 10
while x < y
    x ← x + 2
    y ← y − 1
endwhile
print x, y

true. Third iteration: x=9, y=7, condition 9 < 7 false, loop ends. Final output: 9 and 7.

我们可以追踪循环：初始 x=3, y=10。第一次迭代：x 变为 5，y 变为 9，条件 5 < 9 为真。第二次迭代：x=7, y=8，条件 7 < 8 为真。第三次迭代：x=9, y=7，条件 9 < 7 为假，循环结束。最终输出：9 和 7。

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9. Python Basics: Variables and Data Types | Python 基础：变量与数据类型

In Python, values are assigned to variables using the '=' operator. The data type is determined automatically.

在 Python 中，用 '=' 操作符将值赋给变量。数据类型会自动确定。

Example: name = "Alex" is a string (str), age = 13 is an integer (int), score = 87.5 is a float, and online = True is a Boolean (bool).

例如：name = "Alex"

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